If you are trying to setup-spamexperts-for-external-mail-server, first please white list the below A recorrd or domain on your external mail server.
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mxcluster.cleverspeed.com A 103.3.164.14
mxcluster.cleverspeed.com. A 103.3.164.15
mxcluster.cleverspeed.com A 117.120.2.21
mxcluster.cleverspeed.com A 117.120.2.22
mxcluster.cleverspeed.com A 117.120.2.23
mxcluster.cleverspeed.com A 117.120.4.23
mxcluster.cleverspeed.com A 117.120.5.45
mxcluster.cleverspeed.com A 103.3.164.13
or
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Also, please update the below spam experts SPF record(TXT record), otherwise there will be a chance for a `bounce back message.
TXT >> "v=spf1 ip4:"xxx" a mx a:spf.cleverspeed.com -all"
NB: At the place of xxx include the server IP.
Then create the email account on your mail server and check.